DE. T. DAVIDSON ON RECENT BEACHIOPODA. 241 



Fig. 11. Linyula MurjMana, King, MS. A large example with its pcduuclc; from Morcton Bay, 



Australia (Davidson Coll., Brit. Mus.). 

 Figs. 12, 13. Lingula Mans, Swainson. 12. A fine example with peduncle, after Reeve; China Seas 



(Cuming Coll., Brit. Mus.). 13. A normally-shaped example (Davidson Coll., Brit. Mus.). 



PLA.TE XXX. 



Figs. 1-3. Lingula Murphiana,'\Lmg. 1. Exterior of sliell. 2. Interior of dorsal valve. 3. Interior of 

 ventral valve ; Moretou Bay, Australia (Davidson Coll., Brit. Mus.). 



P^gs. 1—5. Lingula sp. ? Bay of Yeddo, Japan (Davidson Coll., Brit. Mus.). 



Fig. 6. Lingula anatina, Lamarck ; from Japanese Seas, showing extremity of peduucle (Davidson. 

 Coll., Brit. Mus.). 



Figs. 7-10. Young stages of Glottidia Audebarti, Broderip, = L. pyramidata, Stimpson ; after W. K. 

 Brooks (/. c). Fig. 7. Dorsal view of the youngest larva figured, x 250 diameters. Fig. 8. A 

 little older larva. Fig. 9. Dorsal view of somewhat older embryo. Fig. 10. Ventral view of 

 a small Lingula soon after it becomes sedentary. The letters have the same signification in all 

 the figures. A. Dorsal or aboral valve of shell. B. Ventral or oral valve. C. Peduncular 

 or posterior eud of shell. D. Anterior end. a a, hinge-teeth of aboral valve ; 6 />, hiuge-teeth 

 of oral valve ; c, semicircular plate of aboral valve ; d, median tentacle ; d d*, the pair of oral 

 tentacles ; d 2, d 3, d 4:, d i>, the tentacles of one side numbered according to their order 

 of appearance, d, n, the most recent pair of tentacles, in process of development at the sides 

 of the aboral tentacles; e, the lip; /, lateral walls of the body (parietal bands) ; g, body- 

 cavity; A, liver; i, oesophagus ; /;, hepatic chamber of stomach ; /, intestinal chamber of stomach ; 

 ni, intestine ; n, anus ; o, mouth ; p, central and side muscles = at this stage the central, trans- 

 median, and lateral muscles of King ; q q, the lophophore ; r, posterior unpaired muscle, =5r, or 

 umbonal muscle of King; s, peduncle; s*, free end of peduucle; «**, cavity of peduucle; 

 /, pallial cavity; u, ventral end of anterior lateral muscle; m**, dorsal end of transmediau muscles; 

 r, pallial sinus ; iv, its opening into the body-cavity ; x, venti-al portion of nerve-ring, x*, 

 (psophageal commissure ; x**, ganglionic enlargement of x*; x***, otocyst ; //, retractor muscles; 

 z, reflection of the dorsal portion of the body-wall on to the inner surface of the shell. 



Fig. 11. Diagram of longitudinal section of the embryo at stage shown in fig. 9. a, tips of valves; 

 b, thickened margin of mantle ; c, mantle ; d, dorsal median tentacle ; e, lophophore ; /, li p; 

 //, mouth; /(, oral cavity; i, body-cavity; k, wall of oesophagus; /, oesophagus; m, hepatic 

 chamber of stomach ; n, intestinal chamber of stomach ; o, intestine ; q, ventral ganglion ; 

 r, posterior muscle ; s, dorsal valve of shell ; t, ventral valve of shell. 



Figs. 12-1 1. Structures of Glottidia Audebarti, Broderip, = Lingula pyramidata, Stimpson ; after H. G. 

 Beyer (/. c). Fig. 12. Transverse section through lateral body-wall: c.c, ectodermal covering; 

 vac, vacuoles ; I.e., lime-cells ; *./., supporting lamella ; p.e., modified peritoneal epithelium ; 

 r.np., cross-sections of ripe spermatophores ; sp., spermatophores. Fig. 13. Longitudinal 

 section through intestinal canal Ijclow stomach: p.c, dense layer of i)critoncal epithelium; 

 .it., supple layer of supporting lamella; w., wall of intestine; ci/., ciliated internal layer of 

 same. Fig. 14. Transverse section through margin of mantle, shell, and mantle-sinus : cu., 

 cuticle; A., hair ; sh., body of shell diagrammatically represented ; s./., supporting fibres; ec, 

 ectodermal layer lining shell; y.o., young ova; g.r., generative ridge contained within; ni.s., 

 mantle-sinus ; sp., spermatophores ; ni.m., mantle margin ; cc, ectodermal layer ; pL, plexus of 

 corpusculated supporting fibres or " sensory ceils " of Schulgin. 



